1. Field of the Invention
The present invention relates to a defect integrated processing apparatus for performing an integrated processing of light and shade and/or smudgy defects and method thereof.
More particularly, the invention relates to a defect integrated processing apparatus and method for use in inspection of defects on a plain material roll (or web) based on an image data which is produced by an image pick-up camera, picking up an image of the web (e.g., paper, film and nonwoven fabric, etc.) having a certain width and traveling in one direction,
2. Description of the Related Art
Conventionally, various inspection apparatuses are well known. In a typical inspection apparatus, an image of a workpiece such as a web is picked up by using a camera and light-and-shade or minute defects of the workpiece are inspected through the use of an image signal obtained by the camera.
For example, FIG. 16 is a block diagram showing a conventional light-and-shade inspection apparatus 160. Apparatus 160 includes a line-sensor camera 1 for picking up an image of a web 2 as an inspected object having a constant width and traveling in one direction, an illuminator 3 for illuminating a zone R picked up by the camera 1, and an image processing device 4 for processing data of an image picked up by the camera 1 and inspecting a defect on the web.
The line-sensor camera 1 includes, for example, a photodetector array of 1024 elements (e.g., a charge-coupled device (CCD)) disposed along a line. Specifically, the camera 1 is disposed upwardly of a central portion along a width (or transverse) direction of the web so that the photodetectors are arranged in a line array across the web in the transverse (width) direction thereof and in parallel with the transverse direction. The illuminator 3 is disposed downwardly of (e.g., beneath) the web 2 so as to illuminate the zone R to be picked up by the camera 1 from a rear surface of the web 2.
The image processing device 4 detects a light-and-shade defect by judging whether an obtained image data such as a brightness (e.g., luminance) information is more than a predetermined value, or detects low contrast light-and-shade defects such as crevice spots and oil stains, etc., by, as a macro-filter processing, segmenting (e.g., partitioning) an image data at every predetermined range to form a plurality of segments and performing an integration within the respective segments. Thereafter, a differentiation is performed by obtaining respective differences between segments of those integration values, or, functions to detect edges and minute defects by a micro-filter processing, using a differentiating filter processing.
However, such a conventional inspection apparatus 160 is limited to a processing operation for separately or independently detecting those various defects. Thus, in the conventional inspection apparatus, a defect may be detected to be defects of more than one kind on the workpiece (e.g., a defect may be counted as a first type of defect and as a second type of defect, even though the defect constitutes a single defect). As a result, the number of defects may be incorrectly detected (e.g., to be greater than an actual number of defects).
Additionally, it is impossible to know from the detected results which features, such as an actual profile and size, etc., the respective defects as detected have on the workpiece. Further, in the detection of the low contrast light-and-shade defect by using the macro-filter processing, the presence and the absence of defects are detected at each segment (e.g., at a segment unit) defining an integrating range. Consequently, a spatial resolution becomes coarse depending on how segments on the image data are established. Thus, accurately detecting defect positions and sizes is difficult.
In view of the foregoing and other problems of the conventional systems and methods, an object of the present invention is to provide a defect integrated processing apparatus and method thereof capable of precisely detecting and obtaining a defect information including, for example, number, position and/or size of the defects, etc., by integrally processing various kinds of defects.
To overcome the above-mentioned problem and others, in a first aspect, a defect integrated processing apparatus according to the present invention for use in picking up an image of an object to be inspected to obtain an image data and then, based on the image data, inspecting defects on the object in an integrated fashion, includes:
an image pick-up device for picking up an image of an object to output an image data;
a light-and-shade defect detecting portion for detecting light-and-shade defects on the object based on the image data obtained through the image pick-up device;
a minute defect detecting portion for detecting edges and minute defects on the object by performing a differential processing of the image data obtained through the image pick-up device;
a low contrast light-and-shade defect detecting portion for performing a differential processing of an integrated image obtained through an integral processing of the image data obtained through the image pick-up device; and
a defect integrated processing portion for obtaining an integrated information involving defects by performing a processing, in an integrated fashion, of the respective defects of the light-and-shade defects obtained through the light-and-shade defect detecting portion, the minute defects obtained from the minute defect detecting portion, and the low contrast light-and-shade defects obtained through the low contrast light-and-shade defect detecting portion.
With this arrangement, various kinds of defects are processed in an integrated fashion to allow a detailed detection to obtain an accurate defect information about, for example, a number of defects, positions of defects, and/or sizes thereof, etc.
Also, according to the present invention, the light-and-defect detecting portion includes:
a projection operation portion for calculating a projection data by adding together a predetermined number of image data at a given position along a certain direction of the object, which image data are obtained through the image pick-up device;
a background operation portion for calculating a background lightness across a width direction of the object, based on the projection data obtained through the projection operation portion; and
a difference operation portion for removing variations of the background lightness across the width direction obtained through the background lightness operation portion from the image data obtained through the image pick-up device by subtracting a former background lightness from a latter image data.
With this arrangement, variations of the background lightness caused by the camera""s and illuminator""s optical systems and the sizes of defects, can be eliminated precisely, thereby achieving a highly reliable defect integrated processing.
Also, according to the present invention, the background lightness operation portion includes:
a filter for performing a smoothing processing of the projection data across the width direction of the object obtained through the projection operation portion; and
a normalizing portion for calculating the background lightness by dividing the smoothed data through the filter by the predetermined number used for adding together the image data at the given position.
With the projection operation portion, the number of data which are processed through smoothing can be increased substantially, thereby increasing the length of the smoothed data in comparison with the defect size. Therefore, an affect of the defects on the background lightness calculation by the smoothing processing, can be reduced, thereby performing a highly accurate background lightness calculation.
Additionally, the defect integrated processing apparatus, according to the present invention, further may include a comparing portion for comparing the output of the difference operation portion with a predetermined value to detect the light-and-shade defects. With this arrangement, the light-and-shade defects can be detected reliably.
Further, in the defect integrated processing apparatus according to the present invention, the light-and-shade defect detecting portion may include a light-and-shade feature detecting portion for detecting light-and-shade features by establishing on an image based on the image data a mesh pattern of meshes, each mesh being a predetermined size, and then counting the number of pixels, each pixel being present within each mesh and larger than a light defect threshold value and similarly counting the number of pixels, each pixel being present within each mesh and smaller than a shade defective threshold value.
Further, in the defect integrated processing apparatus according to the present invention, the low contrast light-and-shade defect detecting portion may include a macro-filter processing portion, the macro-filter processing portion including:
an integrating operation portion for obtaining an integrated image by dividing an image including image data outputted from the image pick-up device into a plurality of meshes which are of substantially equivalent areas to each other and then adding together the image data present within each divided mesh;
a differentiating; operation portion for obtaining a differentiated image by performing a difference operation at every predetermined interval between meshes in connection with the integrated image obtained by the integrating operation portion; and
a contrast defect detecting portion for detecting low contrast defects based on the differentiated image obtained by the differentiating operation portion.
With such a macro-filter, low contrast light-and-shade defects such as an oil stain, contaminant, mark, etc. can be detected with high accuracy.
Further, in the defect integrated processing apparatus according to the present invention, the low contrast light-and-shade defect detecting portion may include a plurality of macro-filter processing portions similar to the above-mentioned macro-filter processing portion, the macro-filter processing portions being different from each other in mesh size in a range of which the addition of the image data is performed by the integrating operation portion and different from each other in threshold value which is varied dependent on the mesh size and based on which defects are detected by the contrast defect detecting portion.
Furthermore, in the defect integrated processing apparatus according to the present invention, the low contrast defect detecting portion further may include a macro-filter integrated processing portion, the macro-filter integrated processing portion being adapted for, among meshes of different sizes in each range of which the addition of the image data is performed by the integrating operation portion, subtracting from a value of the integrated image having defects and obtained through a smaller mesh size its average value so as to obtain a subtracted value, subtracting the subtracted value from a value of the integrated image obtained through a larger mesh size so as to obtain a differentiated image in the larger mesh size, and, based on the differentiated image, judging and detecting low contrast defects in the larger mesh size.
With this arrangement, for example, a defect detected through a smaller mesh may be prevented from being again detected as another, different defect detected through a larger mesh, thereby preventing counting a defect twice. Thus, the number of defects counted will not include the same, duplicate defect.
Further, in the defect integrated processing apparatus according to the present invention, the macro-filter integrated processing portion is adapted for outputting to the defect integrated processing portion the respective values, as macro-defect features, based on the integrated images involving defects obtained through the macro-filter integrated processing portion as well as the information of mesh positions.
Further, in the defect integrated processing apparatus according to the present invention, the minute defect detecting portion may include:
a micro-filter processing portion adapted for obtaining vertical and horizontal differentiated images of an image based on the image data, calculating an added image which is an average of sum of the vertical and horizontal differentiated images, and highlighting a minute defect by smoothing the added image; and
a micro-filter feature detecting portion adapted for digitizing into binary values the output value from the micro-filter processing portion, establishing a mesh pattern of meshes, each being of a predetermined size on the image based on the image data, and counting the number of pixels, each pixel having the output value which is larger than the threshold value at each mesh.
With this micro-filter, a minute defect such as a liner defect can be detected reliably.
Further, in the defect integrated processing apparatus according to the present invention, the threshold value includes plural kinds of values (e.g., three kinds of values), at each of which the number of pixels is counted.
Further, in the defect integrated processing apparatus according to the present invention, the object to be inspected may include a web having a constant width and traveling in a constant direction, and the image pick-up device may include a line-sensor camera opposed to the object and disposed across the width direction thereof.
Further, in the defect integrated processing apparatus according to the present invention, the defect integrated processing portion may include:
a connectivity analyzing portion adapted for analyzing a connectivity among the light-and-shade defects obtained by the light-and-shade defect detecting portion, the minute defects obtained through the minute defect detecting portion, and the low contrast light-and-shade defects obtained by the low contrast light-and-shade defect detecting portion; and
a defect feature calculating portion adapted for calculating a predetermined feature based on one defect obtained through the connectivity analyzing portion.
With such an arrangement, for example, an area, a height and a width of a circumscribed polygon (e.g., rectangle), an aspect ratio, a compactness, a structure parameter, an edge strength, and an average density which correspond to the number of various defective pixels constituting one defect, may be obtained, thereby to obtain integrated defect information.
Furthermore, in another aspect of the present invention, a defect integrated processing method for picking up an image of an object to be inspected and then, based on its image data, inspecting in an integrated fashion defects of the object, includes:
picking up an image of an object to be inspected to obtain an image data;
based on light-and-shade information of the image data obtained through the image picking-up step, detecting light-and-shade defects of the object;
performing a differential processing of the image data obtained through the image picking-up step to detect edges and minute defects of the object;
performing an integral processing of the image data obtained through the image picking-up step to obtain an integrated image and then performing a differential processing of the obtained integrated image to detect low contrast light-and-shade defects; and
performing a processing in an integrated fashion of the light-and-shade defect, the minute defects, and the low contrast light-and-shade defects detected to obtain an integrated information of defects detected.
The present disclosure relates to subject matter contained in Japanese Patent Application No. 10-205253, filed Jul. 21, 1998, which is expressly incorporated herein by reference in its entirety.